import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  bool flag = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.animation),
        onPressed: () {
          setState(() {
            flag = !flag;
          });
        },
      ),
      appBar: AppBar(
        title: const Text("AnimatedContainer Demo"),
      ),
      body: Center(
        child: AnimatedContainer(
          duration: const Duration(milliseconds: 500),
          // 动画时长500 ms width: flag?100:300,
          height: flag ? 100 : 300,
          color: Colors.blue,

        ),
      ),
    );
  }
}
